"According to the reports forty people have died and 30 to 35 wounded," he said.

The wounded have been rushed to the Dera Ghazi Khan hospital, Sahu told a private television channel.

Local police chief Tasadduq Hayat told AFP by telephone that the bomb exploded outside the shrine.

"It was a bomb blast and it is not clear if it was a suicide attack" he said.

More than 30 people were wounded, he said, adding that details about the death toll were being collected.